#ifndef _MEMDC_H_
#define _MEMDC_H_

//////////////////////////////////////////////////
// CMemDC - memory DC
//
// Author: Keith Rule
// Email:  keithr@europa.com
// Copyright 1996-1997, Keith Rule
//
// You may freely use or modify this code provided this
// Copyright is included in all derived versions.
//
// History - 10/3/97 Fixed scrolling bug.
//                   Added print support.
//
// This class implements a memory Device Context

class CMemoryDC : public CDC {
private:
        CBitmap m_bitmap; // Offscreen bitmap
        CBitmap* m_oldBitmap; // bitmap originally found in CMemDC
        CDC* m_pDC; // Saves CDC passed in constructor
        CRect m_rect; // Rectangle of drawing area.
        BOOL m_bMemDC; // TRUE if CDC really is a Memory DC.
public:
        CMemoryDC(CDC* pDC) : CDC(), m_oldBitmap(NULL), m_pDC(pDC)
        {
                ASSERT(m_pDC != NULL); // If you asserted here, you passed in a NULL CDC.
                
                m_bMemDC = !pDC->IsPrinting();
                
                if (m_bMemDC){
                        // Create a Memory DC
                        CreateCompatibleDC(pDC);
                        pDC->GetClipBox(&m_rect);
                        m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height());
                        m_oldBitmap = SelectObject(&m_bitmap);
                        SetWindowOrg(m_rect.left, m_rect.top);
                } else {
                        // Make a copy of the relevent parts of the current DC for printing
                        m_bPrinting = pDC->m_bPrinting;
                        m_hDC = pDC->m_hDC;
                        m_hAttribDC = pDC->m_hAttribDC;
                }
        }
        
        ~CMemoryDC()
        {
                if (m_bMemDC) {
                        // Copy the offscreen bitmap onto the screen.
                        m_pDC->BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(),
                                this, m_rect.left, m_rect.top, SRCCOPY);
                        //Swap back the original bitmap.
                        SelectObject(m_oldBitmap);
                } else {
                        // All we need to do is replace the DC with an illegal value,
                        // this keeps us from accidently deleting the handles associated with
                        // the CDC that was passed to the constructor.
                        m_hDC = m_hAttribDC = NULL;
                }
        }
        
        // Allow usage as a pointer
        CMemoryDC* operator->() {return this;}
        
        // Allow usage as a pointer
        operator CMemoryDC*() {return this;}
};

#endif
